What does Langdon think about the nature of Da Vinci's work?

As far as Da Vinci's work is concerned, Langdon believes Da Vinci was a proponent of feminine sensibilities and promoted his beliefs through the painting. Langdon believes Da Vinci's Mona Lisa, for example contains a message of androgyny by making her name an anagram for the male and female Egyptian gods of fertility, "AMON" and "L'ISA". Langdon believes that all of Da Vinci's works are full of similar hidden meanings and messages.